Pisces called
Ichtyes ("the fishes") by the Greeks, "Pisces" being the Latin translation.

In the constellation
of Pisces there's a big fish and a little fish. In Greek mythology Aphrodite
and her son, Ichthus (some versions say the god Eros was her son), were being
pursued by a huge monster fish by the name of Typhon.

In order to escape
their nasty, monstrous pursuer, Aphrodite turns herself and her son into fishes.
Together they then hid from the monster fish, Typhon, in the Euphrates River.
Aphrodite (symbolizing in this case "the great mother") is the big fish and
Ichthus is the small fish...